Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753911AbbFDVEL (ORCPT ); Thu, 4 Jun 2015 17:04:11 -0400 Received: from h1446028.stratoserver.net ([85.214.92.142]:60625 "EHLO mail.ahsoftware.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752508AbbFDVEB (ORCPT ); Thu, 4 Jun 2015 17:04:01 -0400 Message-ID: <5570BD32.9020705@ahsoftware.de> Date: Thu, 04 Jun 2015 23:03:46 +0200 From: Alexander Holler User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.6.0 MIME-Version: 1.0 To: Rob Clark , Tomeu Vizoso CC: "linux-arm-kernel@lists.infradead.org" , Mark Rutland , Linux Fbdev development list , linux-usb@vger.kernel.org, linux-pwm@vger.kernel.org, "dri-devel@lists.freedesktop.org" , Thierry Reding , linux-i2c@vger.kernel.org, linux-clk@vger.kernel.org, "moderated list:ARM/S5P EXYNOS AR..." , Grant Likely , "devicetree@vger.kernel.org" , linux-pm@vger.kernel.org, linux-gpio@vger.kernel.org, Rob Herring , "linux-tegra@vger.kernel.org" , Dan Williams , =?UTF-8?B?U3TDqXBoYW5lIE1hcmNoZXNpbg==?= , Dmitry Torokhov , Linux Kernel Mailing List , dmaengine@vger.kernel.org Subject: Re: [PATCH 00/21] On-demand device registration References: <1432565608-26036-1-git-send-email-tomeu.vizoso@collabora.com> In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2887 Lines: 59 Am 03.06.2015 um 23:12 schrieb Rob Clark: > On Mon, May 25, 2015 at 10:53 AM, Tomeu Vizoso > wrote: >> Hello, >> >> I have a problem with the panel on my Tegra Chromebook taking longer than >> expected to be ready during boot (Stéphane Marchesin reported what is >> basically the same issue in [0]), and have looked into ordered probing as a >> better way of solving this than moving nodes around in the DT or playing with >> initcall levels. >> >> While reading the thread [1] that Alexander Holler started with his series to >> make probing order deterministic, it occurred to me that it should be possible >> to achieve the same by registering devices as they are referenced by other >> devices. >> >> This basically reuses the information that is already implicit in the probe() >> implementations, saving us from refactoring existing drivers or adding >> information to DTBs. >> >> Something I'm not completely happy with is that I have had to move the call to >> of_platform_populate after all platform drivers have been registered. >> Otherwise I don't see how I could register drivers on demand as we don't have >> yet each driver's compatible strings. >> >> For machs that don't move of_platform_populate() to a later point, these >> patches shouldn't cause any problems but it's not guaranteed that we'll avoid >> all the deferred probes as some drivers may not be registered yet. >> >> I have tested this on boards with Tegra, iMX.6 and Exynos SoCs, and these >> patches were enough to eliminate all the deferred probes. >> >> With this series I get the kernel to output to the panel in 0.5s, instead of 2.8s. > > So, complete drive-by comment (and I won't claim to be a DT expert, > etc, etc, so take this with a few grains of salt), but why not push > the problem to the DT compiler (or a pre-process step that could be > run on existing DT blobs), which generates an optional DT node that is > the recommended probe order? That seems like it avoids adding > complexity into the early boot code (which seems like a good thing).. I've played with that approach too (as my patches for dtc do contain the same code I've put into the kernel, but decided that it doesn't make much sense. The sort algorithm is really small (some dozen lines), very fast (around 3-5ms on a omap) and might be later used to sort necessary module loading too. So there would be no advantage to put a sorted list into the DT. And having the sort algorithm in the kernel, would make it possible to use it for acpi or something else too, if they manage it to provide the necessary dependencies. Regards, Alexander Holler -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/